To extinguish the flame the turn-off button is pressed, when a second magnet (not shown in cut) lifts the armature and twists it in the opposite direction, so that when the circuit is broken the armature falls free to its normal position, closing the valve.
Fig. 58.
In wiring up an automatic burner it is necessary to run two wires to it, one from the white button and another from black button on push plate S. Reference to Fig. 58 will make this clear. Most burners are provided with two binding posts inside the brass case, and the wires are run through a rubber-bushed hole in the base. If the push has already been set in position and wired up, as per Fig. 58, have the buttons pressed alternately, when on touching the binding posts on automatic with the wires, the lighting or extinguishing connection is easily selected. The lighting armature in most automatic burners buzzes violently, while the extinguishing one only strikes once on contact being made. Fig. 58 shows how to connect up two pushes to one automatic, one push, perhaps, being located downstairs and the other upstairs in the case of a hall lamp. In setting up these burners care must be taken not to bend contacts or alter adjustment, and absolute precaution is necessary that no crosses or weakly insulated places are in circuit. After burning for some time it often happens that the burner refuses to light, only buzzing feebly or not at all. If feebly, the trouble is in battery, which should consist of, at least, four or six cells of open circuit battery with low internal resistance, such as Samson-Law carbon cylinder, or for occasional use large, dry cells.
If no click is heard on pressing white button, examine all connections; if still no trouble is found, examine the platinum break. The platinum tip may be bent by the continual hammering against the platinum tip on vibrating rod, preventing contact on collar, or that soot has formed there. These are the commonest maladies of automatic burners, and can be easily remedied by readjusting platinum tip and cleaning. Contacts here must be clean. In general wiring use waterproof office wire or, better still, rubber-covered wire; for fixtures use the fixture wire before described. When shellacking the wire to the fixture don't attempt to connect up batteries until the shellac is dry and hard, say for half a day. Electric gas-lighting is fruitful of trouble if the work is not well done. Another cause of trouble may arise from a dirty burner not allowing the gas to strike near the contact (clean the burner), or the collar carrying contact may have shifted, perhaps short-circuited; it should be insulated with a thin strip of asbestos. Although white lead at the joints makes a fairly good contact, some persons prefer to use tin-foil, a piece of foil being worked around screw thread and the burner screwed on; it prevents leaks as well as lead if well done, and makes better contact. As a short circuit on the wires will cause all the burners to fail, many devices have been invented to open the circuit upon such an occurrence. These will be found described in the catalogues of electrical stores; they do not come within the province of this book for description.
CHAPTER X.
BATTERIES FOR COILS.
In selecting a battery to operate the coil, one is needed which will supply a large steady current for a considerable period. Although the primary circuit is opened and closed rapidly, yet the class known as open circuit cells is not suitable, even though they have a low internal resistance, and thereby render a large current. Such cells are only suitable for the uses for which they are mostly designed, bell-ringing or annunciator work. There is one case, however, where an open circuit cell may be used with an induction coil, and that is in gas lighting as previously described; but here a dozen or so impulses of current are generally sufficient, followed by long periods of rest. For the latter work the cells in common use are the Samson, Champion, and Monarch, all of which are of low internal resistance and great recuperative power.
The reason that such cells will not work for long periods, is that they polarize. This latter action takes place in these open circuit cells, which are of the Leclanché type as follows: A positive plate of zinc is immersed in a solution of ammonium chloride (or salammoniac), and a negative plate of carbon and peroxide of manganese, contained either in a porous cup or compressed into a block also stands in the solution. Care is taken that these two plates do not touch each other. When the outside circuit is closed the zinc combines with the chlorine of the solution liberating free hydrogen and ammonia. The hydrogen appears at the negative plate, where it is acted upon by the oxygen of the peroxide of manganese to form water.